Truck is a 1979 F250 4x4 351M c6

Has a good running 351M but it's tired and leaks from every where so needs a going through but most accessories are new on it. Does any of the accessories fit on a 460?

Is it worth it to spend the extra money on a 460 (can't verify is it runs) all accessories are gone so just block and heads, is it worth it or should I just keep the 351M for now and redo it?

I don't need much power, more reliability is better. Not very experienced in these motors so looking for some advice.
Thanks

 

While things like the PS pump or AC compressor might be the same, the mounts will be different, and the lines in and out will probably be different.

A 460 swap is a bit of work. While it will bolt up to your trans, exhaust, cooling and a lot of other little things are different. It is not a "bolt in direct swap".

Your 351M can be brought back to life for a lot less time and maybe even money than a 460 swap.

Serving suggestion:

--pull and tear it down

--have the block hot tanked

--hone it & re-ring it if the pistons are in spec.

--put in new standard bearings

--new valve seals in the heads, after you make sure the valves are all ok

--put it back together with a new cam that actually moves and holds the valves open and a timing set that runs the cam "straight up".

Drive it.

M-Block 351M/400 Performance

You will enjoy a bit more power and this should not break the bank.

 

Agreed.

If you want to spend a bit more to turn it into a 400, all you'd need is a 400 crank and pistons....but definitely a better cam and straight up double roller timing chain.

 

Ya I thought about a 400 build, I would definitely consider it depending on how far down I strip the motor. Might just do valve job, cam, gaskets and seals and change the timing so it's not at it's emission restricted state.

 

If you are going that far, it isn't a whole lot more trouble or money to do the lower end.

Robert

 

i have rebuilding my 351/m to a 400 with all the parts and machine work is costing about 2000.00 that not including perfomer intake or carb.

 

if your lower end is still good, you could work your heads, get an rv cam with timing chain, headers, aluminum intake, 600 cfm carb, and you could be seeing 300+hp out of that 351m....

 

. Old thread from October, but prolly didn't do anything over winter... 351M's have way low compression ratio... so a bigger cam does no good... weakens lower RPMs power, throttle response, and hurts the already bad MPG... also, there are no good off-the-shelf, reasonably priced rebuilder pistons for a 351M, they lower compression ratio even further... putting a 400 crank into a 351M turns it back into a 400" and there are good, reasonably priced off-the-shelf pistons available for them now from TMI/KB... this makes the engine more efficient yielding improved MPG and power and throttle response when used with a mild performance cam... or even the stock cam advanced to straight up timing... re-use all accessories... will put a huge smile on your face...! Also, 80 lbs. lighter engine than a 460 and better MPG...